Imagine this: let’s say the writers themselves do understand the highest level of competence. They write the Voyager crew in a way so that they handle all issues perfectly. How would it be possible for them to come up with any situation where this Voyager crew is challenged? - they can’t. Because they are portraying them as perfectly competent, which is based in the writer’s imagination, the definition of this perfect competency is that the writers could not come up with a way for them to be challenged.

Sorry but this assumption doesn’t hold up. You can still face difficult odds while doing everything competently. It’s one of Picard’s best quotes: “It is possible to commit no mistakes and still lose. That is not a weakness; that is life.”. You can be absolutely perfect, but good luck beating a Q when it doesn’t want to humour you.